Many, if not all, active implantable medical devices are hermetically sealed so that, among other things, internal electrical components are fluidly isolated from bodily fluids of the patients when the devices are implanted. The hermetic seal of such devices is typically tested by the manufacturer.
Such testing often involves leak testing, in which the presence of a gas placed within the hermetically sealed device is detected external to the device. In some situations, a non-hermetically sealed device is placed in an environment containing the gas, such as in a helium glove box, and the housing of the device is hermetically sealed within the environment. Thus, the hermetically sealed housing is filled with the gas, such as helium, in the environment. The device is determined to not be hermetically sealed if the gas, or a threshold level of the gas, external to the device is detected during the leak testing.
Some devices may contain material that can sorb and release the gas to be detected. When such materials are located external to a hermetically sealed housing, they can interfere with leak testing. For example, if the external materials are present in the environment containing the gas, such as a helium glove box, while the housing is being hermetically sealed, the external materials may sorb the gas during sealing and later release the gas during leak testing. The release of the gas by the external material during leak testing can result in a false positive result for a leaky seal.